Retarded PDI diffusion and a reductive shift in poise of the calcium depleted endoplasmic reticulum

BMC Biology

Research Article

Eduardo Pinho Melo¹  Romain Laine²  Weiyue Chen²  Clemens F Kaminski²  Ryo Ushioda³  Kazuhiro Nagata³  Edward Avezov⁴  Tasuku Konno⁴  Ana Crespillo-Casado⁴  Heather P Harding⁴  David Ron⁴  Alisa Zyryanova⁴ 

[1] Center for Biomedical Research, Universidade do Algarve, Faro, Portugal;Department of Chemical Engineering and Biotechnology, University of Cambridge, CB2 3RA, Cambridge, UK;Faculty of Life Sciences, Kyoto Sangyo University, 603-8555, Kita-Ku, Kyoto-City, Japan;University of Cambridge, Cambridge Institute for Medical Research, Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, CB2 0XY, Cambridge, United Kingdom;

关键词: Fluorescence lifetime imaging;    Protein disulfide isomerase;    Calreticulin;    Endoplasmic reticulum;    Redox;    Calcium;   

DOI  :  10.1186/s12915-014-0112-2

 received in 2014-11-04, accepted in 2014-12-23,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundEndoplasmic reticulum (ER) lumenal protein thiol redox balance resists dramatic variation in unfolded protein load imposed by diverse physiological challenges including compromise in the key upstream oxidases. Lumenal calcium depletion, incurred during normal cell signaling, stands out as a notable exception to this resilience, promoting a rapid and reversible shift towards a more reducing poise. Calcium depletion induced ER redox alterations are relevant to physiological conditions associated with calcium signaling, such as the response of pancreatic cells to secretagogues and neuronal activity. The core components of the ER redox machinery are well characterized; however, the molecular basis for the calcium-depletion induced shift in redox balance is presently obscure.ResultsIn vitro, the core machinery for generating disulfides, consisting of ERO1 and the oxidizing protein disulfide isomerase, PDI1A, was indifferent to variation in calcium concentration within the physiological range. However, ER calcium depletion in vivo led to a selective 2.5-fold decline in PDI1A mobility, whereas the mobility of the reducing PDI family member, ERdj5 was unaffected. In vivo, fluorescence resonance energy transfer measurements revealed that declining PDI1A mobility correlated with formation of a complex with the abundant ER chaperone calreticulin, whose mobility was also inhibited by calcium depletion and the calcium depletion-mediated reductive shift was attenuated in cells lacking calreticulin. Measurements with purified proteins confirmed that the PDI1A-calreticulin complex dissociated as Ca2+ concentrations approached those normally found in the ER lumen ([Ca2+]K0.5max = 190 μM).ConclusionsOur findings suggest that selective sequestration of PDI1A in a calcium depletion-mediated complex with the abundant chaperone calreticulin attenuates the effective concentration of this major lumenal thiol oxidant, providing a plausible and simple mechanism for the observed shift in ER lumenal redox poise upon physiological calcium depletion.

【 授权许可】

CC BY   
© Avezov et al.; licensee BioMed Central. 2015